1. Field of the Invention
The present invention relates to a scanner, and more particularly, to a multiple resolution scanner comprising device and method for determining its resolution.
2. Description of the Prior Art
A multiple resolution scanner commonly comprises a lens module which has several lenses with different resolutions movably installed in the scanner. Moving or rotating the lenses allows changing of the resolution of the scanner. The lens module further comprises more than one lens detector for detecting the positions of the lenses to determine which resolution is currently being used.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a prior art lens module 10. The lens module 10 comprises two lens detectors 12,13 for detecting the lens currently in use. The lens detector 12 is used for detecting a first lens 14 and the lens detector 13 is used for detecting a second lens 16. When the lens detector 12 detects that the first lens 14 is in use, it generates a detecting signal to indicate that the resolution of the first lens 14 is the present resolution of the lens module 10. Similarly, when the lens detector 13 detects that the second lens 16 is in use, it generates a detecting signal to indicate that the resolution of the second lens 16 is the present resolution of the lens module 10. The resolution of the lens module is determined based on the signal of the lens detector 12 or 13, therefore if the lens detectors 12,13 are worn out, it will be impossible to determine the resolution of the lens module 10. Moreover, if there are additional lenses of differing resolutions in the lens module 10, the structure becomes more complicated thus driving up costs.